As you can see, the future takes the same subjunctive form as the present. The subjunctive does however, take a different conjugation in the past tense. Let’s take a look at how these work for regular ‘ar’, ‘er’ and ‘ir’ verbs:

You can use the past subjunctive when you wish for something in order to be able to achieve something.

Si yo fuera más joven, lo habría hecho – If I were younger, I would have done itSi ella tuviera más dinero, viajaría a París – If she had more money, she would travel to FranceSi yo hubiera sabido que tú estarías aquí, te habría traído un regalo – If I knew you would be here, I would have brought you a giftOjalá supiera lo que le pasó a David – If only I knew what happened to DavidOjalá tuviera dos semanas más the vacaciones – If only I had 2 more weeks of vacation

You can also use ‘haber’ to form the present perfect subjunctive or the pluperfect subjunctive

Me alegro que hayas llegado – I am glad that you have arrivedEsperamos que ustedes ya hayan comido – We hope you have already eatenSi yo hubiera tenido más tiempo, habría visitado a Carlos – If I had had more time, I would have visited CarlosSi me hubieras traído algo especial, te habría perdonado – If you had brought me something special, I would have forgiven youÉl quería que hubieran llegado antes – He wanted them to have arrived before Yo habría preferido que me lo hubieras dicho antes – I would have prefered it if you had told me before